Question

Saltatory conduction of impulse occurs in (a) liver cells (b) non-myelinated nerve fibres (c) myelinated nerve fibres (d) none of these.

Short answer

Saltatory conduction of impulse occurs in (c) myelinated nerve fibres.

Step-by-step solution

Understanding Saltatory Conduction

Saltatory conduction refers to the way electrical signals travel along myelinated neurons. In these neurons, the myelin sheath acts as an insulator, and signals 'jump' from one node of Ranvier (gaps in the myelin sheath) to the next, which speeds up signal transmission.

Identifying Cell Types

To identify which of the listed options is capable of saltatory conduction, one must know the types of cells or fibers that are myelinated. Liver cells are not neurons, non-myelinated nerve fibers refer to neurons without a myelin sheath, and myelinated nerve fibers are neurons with a myelin sheath.

Choosing the Correct Answer

Since saltatory conduction occurs in myelinated nerve fibers due to the presence of the myelin sheath, the correct answer is (c) myelinated nerve fibres.

Key concepts

Myelinated Nerve Fibres

At the heart of rapid neural communication lies the phenomenon of myelinated nerve fibres. Picture the nervous system as a complex network, echoing with electrical impulses that carry messages across the body. Myelin, a fatty substance, wraps around nerve fibres in segments, forming a protective coating known as the myelin sheath. This sheath isn't continuous; it's spaced out at intervals, leading to exposed sections of the nerve fibre.

Think of myelinated nerve fibres as electrical wires wrapped in insulation. Just as proper insulation allows for efficient transfer of electricity along wires, the myelin sheath enables faster and more efficient signal transmission along the nerve fibre. It also helps in maintaining the integrity of the signal, so that the body's messages maintain their clarity and strength as they travel. Without myelination, neural impulses would slow down significantly, hindering our ability to react quickly to stimuli.

Neural Impulse Transmission

Understanding how nerve signals zip through the body at lightning speeds is fascinating. Neural impulse transmission is a complex dance of electrical and chemical signals. In a process called action potential, neurons fire signals that travel along their axons. It's like dominoes falling in a line—once one segment fires, it triggers the next.

In unmyelinated nerve fibres, this action potential moves in a continuous wave, a bit like a fire burning along a fuse. However, in myelinated nerve fibres, the action potential has a more efficient path. Due to the insulating properties of myelin, the impulse leaps from node to node. This 'leaping' significantly increases the speed of impulse transmission, enabling quick reflexes and rapid communication within the nervous system.

Nodes of Ranvier

The gaps in the myelin sheath known as the Nodes of Ranvier play a crucial role in saltatory conduction. These nodes are the exposed sections of the neuron's axon, and they're the stage for a remarkable process. Between the myelinated stretches of the nerve fibre, the nodes are rich in sodium channels.

As the neural impulse reaches a node, it triggers the opening of these channels, causing a rush of ions that keep the action potential going strong. Then, the electrical signal jumps to the next node, bypassing the insulated segments of the axon. This leapfrogging from node to node, rather than a continuous wave, allows for speedier transmission of impulses and is a beautifully orchestrated biological adaptation that underpins quick and efficient neural communication.